Synaptic plasticity in cortical systems

Klintsova, Anna Y.; Greenough, William T.

doi:10.1016/s0959-4388(99)80028-2

Cited by 217 publications

(132 citation statements)

References 75 publications

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“…However, analysis of the pattern of qualitative limb movements (missed aims, failed advances) in recovered animals revealed no fundamental differences from intact animals, suggesting that a purely behavioral compensation was a less likely mechanism of recovery, although more extensive analysis of fine features of qualitative limb use (7) would be required to draw firm conclusions. It is also possible that structural rearrangements of axons, dendrites, or synapses in fact underlie some cases of behavioral ''compensation'' (36,37).…”

Section: Discussionmentioning

confidence: 99%

Spontaneous corticospinal axonal plasticity and functional recovery after adult central nervous system injury

Weidner

Ner

Salimi

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

485

346

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Although it is believed that little recovery occurs after adult mammalian spinal cord injury, in fact significant spontaneous functional improvement commonly occurs after spinal cord injury in humans. To investigate potential mechanisms underlying spontaneous recovery, lesions of defined components of the corticospinal motor pathway were made in adult rats in the rostral cervical spinal cord or caudal medulla. Following complete lesions of the dorsal corticospinal motor pathway, which contains more than 95% of all corticospinal axons, spontaneous sprouting from the ventral corticospinal tract occurred onto medial motoneuron pools in the cervical spinal cord; this sprouting was paralleled by functional recovery. Combined lesions of both dorsal and ventral corticospinal tract components eliminated sprouting and functional recovery. In addition, functional recovery was also abolished if dorsal corticospinal tract lesions were followed 5 weeks later by ventral corticospinal tract lesions. We found extensive spontaneous structural plasticity as a mechanism correlating with functional recovery in motor systems in the adult central nervous system. Experimental enhancement of spontaneous plasticity may be useful to promote further recovery after adult central nervous system injury. Many central nervous system (CNS) lesions lead to functional deficits that fail to improve over time. Yet, spontaneous improvement in motor, sensory, or other neurological function occurs in 41% of patients who sustain spinal cord injuries (1, 2) and in a large proportion of patients with strokes (3, 4) and head trauma (5). Although some of this improvement seems to result from rapid resolution of diaschisis (transient disruption of electrical transmission) or from functional compensation (use of uninjured systems to compensate for injured pathways) (6, 7), a significant proportion of functional recovery occurs over a more protracted time period of several weeks to months. This protracted recovery phase results in restitution of original patterns of the disrupted function, often at a less complete level compared with the preinjured state. However, mechanisms underlying long-term recovery are unknown.The existence of spontaneous recovery over longer time periods raises the possibility that intrinsic structural rearrangements may occur after injury to the adult mammalian CNS. Previous studies have demonstrated that lesions of adult sensory and motor cortex, hippocampus, or red nucleus are followed by compensatory collateral sprouting of axons (8-16), although these compensatory changes have not been correlated with functional recovery.The present study examined mechanisms underlying recovery after lesions of an important motor system in animals, the corticospinal projection to the spinal cord. The corticospinal system was examined because of its well-defined anatomical and functional properties (17-19), its relevance to human injury, and its frequent targeting in efforts to promote regeneration after injury (20-24). The corticospinal tract (CST...

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Section: Discussionmentioning

confidence: 99%

Spontaneous corticospinal axonal plasticity and functional recovery after adult central nervous system injury

Weidner

Ner

Salimi

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

485

346

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“…The dendritic spines are, in fact, the site where duplication of synaptic spines associated with long-term potentiation (LTP) and learning may occur (30,31) and are also the site where the stimulation of protein synthesis associated with LTP and learning may take place (28,29). Studying the function of the gene product (FMRP) lacking in the fragile X mental retardation, Greenough and colleagues (28,29) have shown that this protein is synthesized at synapses in response to glutamate receptor activation, a process that facilitates learning and regulates LTP induction. FMRP, in turn, catalyzes the postsynaptic assembly of polyribosomes, targeting newly synthesized mRNA to synapses, in a process that may be essential to normal maturation and pruning of synaptic spines.…”

Section: Discussionmentioning

confidence: 99%

Colocalization of integrin receptors and reelin in dendritic spine postsynaptic densities of adult nonhuman primate cortex

Rodríguez

Pesold

Liu

et al. 2000

Proceedings of the National Academy of Sciences

117

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The expression of telencephalic reelin (Reln) and glutamic acid decarboxylase mRNAs and their respective cognate proteins is down-regulated in postmortem brains of schizophrenia and bipolar disorder patients. To interpret the pathophysiological significance of this finding, immunoelectron microscopic experiments are required, but these cannot be carried out in postmortem human brains. As an alternative, we carried out such experiments in the cortex of rats and nonhuman primates. We found that Reln is expressed predominantly in layer I of both cortices and is localized to bitufted (double-bouquet), horizontal, and multipolar ␥-aminobutyric acid-ergic interneurons, which secrete Reln into extracellular matrix. Reln secretion is mediated by a constitutive mechanism that depends on the expression of a specific signal peptide present in the Reln carboxy-terminal domain. Extracellular matrix Reln is found to aggregate in proximity of postsynaptic densities expressed in apical dendrite spines, which include also the ␣3 subunit of integrin receptors. Most pyramidal neurons of various cortical layers express the mouse-disabled 1 (Dab1) protein, which, after phosphorylation by a soluble tyrosine kinase, functions as an adapter protein, probably mediating a modulation of cytoskeleton protein expression. We hypothesize that the decrease of neuropil and dendritic spine density reported to exist in the neocortex of psychiatric patients may be related to a down-regulation of Relnintegrin interactions and the consequent decrease of cytoskeleton protein turnover.glutamic acid decarboxylase ͉ schizophrenia ͉ bipolar disorders ͉ long-term potentiation

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“…In our model, the total energy E (or total current) can be identified with the mean value of the field, E = i h i . The second mechanism is that by which synaptic growth is stimulated by local electrical activity [6,7]. This would correspond here, for a given neuron i, to the field it feels, h i .…”

Section: The Modelmentioning

confidence: 99%

“…Another interesting feature is synaptogenesis, which has been related to various interacting local influences such as the concentration of different neurotransmitters and electrical stimulation [6,7]. On the other hand, synapses can suffer atrophy and die, probably if not potentiated enough by use.…”

Section: Introductionmentioning

confidence: 99%

Development of Neural Network Structure with Biological Mechanisms

Johnson

Marro

Mejías

et al. 2009

Lecture Notes in Computer Science

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Abstract. We present an evolving neural network model in which synapses appear and disappear stochastically according to bio-inspired probabilities. These are in general nonlinear functions of the local fields felt by neurons-akin to electrical stimulation-and of the global average field-representing total energy consumption. We find that initial degree distributions then evolve towards stationary states which can either be fairly homogeneous or highly heterogeneous, depending on parameters. The critical cases-which can result in scale-free distributions-are shown to correspond, under a mean-field approximation, to nonlinear drift-diffusion equations. We show how appropriate choices of parameters yield good quantitative agreement with published experimental data concerning synaptic densities during brain development (synaptic pruning).

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Synaptic plasticity in cortical systems

Cited by 217 publications

References 75 publications

Spontaneous corticospinal axonal plasticity and functional recovery after adult central nervous system injury

Spontaneous corticospinal axonal plasticity and functional recovery after adult central nervous system injury

Colocalization of integrin receptors and reelin in dendritic spine postsynaptic densities of adult nonhuman primate cortex

Development of Neural Network Structure with Biological Mechanisms

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